Nearly 11 million U.S. adults 65 years of age or older have diabetes and this number is expected to increase to about 50 million by the year 2050. Type 2 diabetes patients are at increased risk for atherosclerosis and cardiovascular morbidity. A key early event in atherosclerosis development and progression is impaired vascular endothelial function, which is commonly present in older adults with type 2 diabetes. Aerobic exercise training is a recognized strategy for reducing the risk for cardiovascular disease, but there is still controversy regarding the optimal exercise training program for improving vascular endothelial function in older diabetic patients. We hypothesize that high intensity interval trainig (HIIT) will be more effective compared with moderate intensity continuous training (MICT) in improving vascular endothelial function in older adults with type 2 diabetes. The primary objective of this study is to determine in 65 to 79 year-old adults with type 2 diabetes, the effec of 8 weeks of supervised HIIT and MICT Airdyne exercise on 1) vascular endothelial function (brachial artery flow- mediated endothelium-dependent dilation); 2) vascular endothelial cell protein expression of key factors that influence endothelial function (vascular endothelial cell biopsy coupled with quantitative immunofluorescence); and 3) systemic blood markers of oxidative stress and inflammation. HIIT and MICT are designed to provide equal volume of training (i.e., isocaloric) and will be performed on Airdyne bicycles 4 days/week for 8 weeks. MICT will consist of 47 min of Airdyne exercise at 70% of maximal heart rate (HRmax). HIIT will consist of 40 min Airdyne exercise: 1) short bursts (4 intervals at 4 min each) at high intensity (90% of HRmax) interspersed with recovery periods (3 intervals at 3 min each) at moderate intensity (70% of HRmax); and 2) 10 min warm up and 5 min cool down at moderate intensity (70% of HRmax). This translational new pilot study fits well within the current R21 funding opportunity announcement PAS-11-280: Translational Research: novel interventions for prevention and treatment of age-related conditions. The current application in older adults with type 2 diabetes will significantly impact the field by: 1) establishing the efficacy of HIIT on improving endothelial function, a clinically important outcome strongly linked with atherosclerosis progression and future cardiovascular events; 2) optimizing exercise prescription for preventing and treating atherosclerosis in older adults with type 2 diabetes; 3) providing initial mechanistic insight into the exercise-associated adaptations in vascular endothelial cell protein expression of key factors that influence endothelial function using a novel translational physiology research technique; and 4) providing the scientific basis for designing a larger comprehensive future study to directly investigate the mechanisms of the exercise-induced vascular adaptations.